The Troublesome Trucks (called Cars, originally known as Foolish Freight Cars, in the US narration) are always nicknamed so because they can be very troublesome, and love to play tricks on the engines, barring Edward, Stepney, Hiro, and Salty. The trucks have been the cause of most of the railway's accidents. However, since Douglas smashed the Spiteful Brake Van and Oliver pulled S.C. Ruffey, their leader, apart, they have been frightened of some engines.

The trucks also pulled Thomas down a hill into Salty and got James covered in melons.

The trucks teased James when he smashed them into the snow. When the Pack was building a new bandstand, they refused to move until Percy used his "do-as-I-say" whistle. They have since been good, but they soon decided to put a stop to their good streak by pulling Thomas and Percy down a hill and causing Stephen to get trapped in Ulfstead Mine. They have since been troublesome after this incident.

Thomas had once accidentally shunted them too hard and were just as confused as everyone else when Thomas blamed an imaginary engine named Geoffrey. They also laughed at Den when he was working at the quarry when Mavis was being repaired.

Persona

Every wise engine knows trucks cannot be trusted. Trucks could be considered the rebels and the troublemakers of all rolling stock on the railway, as most of them love to cause mischief and trouble and show no remorse for whatever they do unless told off by their engine. If an engine is having a bad day, makes a mistake, or is easily played upon, the trucks begin their wild antics of singing, name calling, holding back, shoving, bumping, giggling and so on. They will play tricks on an engine based on how they treat them. Most accidents caused by the trucks are a form of revenge due to mistreatment and they are not known for considering the consequences of their actions; they will carry out their plans even if they result in derailing, damaging or destroying themselves.

Trucks can also be described as territorial; when they get used to certain engines pulling them, another engine in the yard to take them may cause confusion or anger for the trucks. In Percy's Predicament for example, Toby and Percy switched jobs, making Toby's trucks furious and causing Percy to crash. In Oliver Owns Up, the trucks refused for Oliver to take them and demanded Duck, Donald or Douglas instead.

To the trucks, one engine is as good as another, as on one occasion they took their anger out on Thomas when they could not get back at James for bumping them.

During the thirteenth - sixteenth seasons, they behaved unusually well but were easily annoyed. From King of the Railway onwards, they have gone back to their old personalities, misbehaving and causing accidents.

Bases

The Troublesome Trucks are based on 5 and 7-plank open wagons.

Livery

All the Troublesome Trucks are painted grey. Previously in the Railway Series and Model Series, they were seen in many liveries such as blue, red, green, yellow, orange, pink, brown and black. Privately-owned Troublesome Trucks typically have their own specific livery.

Hisao Egawa (Japan; Haunted Henry, A Surprise for Percy, Salty's Secret, Harvey to the Rescue, Buffer Bother, Edward the Very Useful Engine, The Spotless Record, James Gets a New Coat, Emily's New Route and Fish)

Nobuaki Kanemitsu (Japan; Emily Knows Best, Saving Edward, Hector the Horrid!, James Works it Out, Percy and the Bandstand, Ho Ho Snowman, No More Mr. Nice Engine, The Smelly Kipper, Tale of the Brave, Missing Gator, Who's Geoffrey?, Salty All At Sea, Henry Gets the Express, Diesel and the Ducklings and Bradford the Brake Van)

Mitsuhiro Sakamaki (Japan; Emily Knows Best, Missing Gator and The Other Side of the Mountain)

Trivia

From the sixth season onwards in the US, the term "truck" is used more often. In more recent seasons, however, the US has been more consistent in using the term "car", unless referring to the trucks with faces.

The audio clip of the trucks laughing heard from the second through seventh seasons is actually Junior Campbell's laughing sound in a higher-pitch, as is the clip of the trucks singing their song, "Pop Goes the Diesel".

This makes the trucks the first characters to have individual voice actors in English-speaking countries.

In the first season the Troublesome Trucks had paper eyes and a paper mouth similar to how Annie and Clarabel's were made. This however, disabled the trucks from having multiple emotions until the second season.

The Troublesome Trucks went through several aesthetic changes in the television series:

Season 2:

The Trucks gained face masks to allow a greater variety of facial expressions, some Season 1 trucks do still appear in the second season however.

Season 12:

The Trucks have the same face design.

Season 13:

The trucks now have slightly different noses from each other (though they retain the same basic face design).

The open topped wagons became taller.

The black and grey trucks seem to be the only ones that have faces.

Season 14:

The Trucks' faces disappear, leaving all trucks without faces.

Season 16:

The grey and black trucks regain their faces.

Season 17:

All trucks are now grey.

The trucks now have identical faces with no distinguishing features, just as they did in the twelfth season.

Season 20:

The Goods Vans regain their faces.

Journey Beyond Sodor:

The tankers and salt vans regain their faces.

Up-scaled narrow gauge slate trucks were introduced, with an entirely new face design.

The trucks were to have a larger role in Thomas and the Magic Railroad, but they were cut from the final film.

Until King of the Railway, the Troublesome Trucks caused no accidents after the ninth season episode, Emily Knows Best and had no speaking roles after the twelfth season.

According to the Railway Series book, Oliver the Western Engine, ballast trucks are considered to be the worst of all.

Between the eighth and nineteenth seasons, only the open wagons were referred to as "Troublesome Trucks".

In both the UK and US narrations of the CGI Series, the trucks have American accents, apart from one truck in Tale of the Brave who had a British accent.

From the first season to the fifth season, the wagons and Troublesome Trucks used in the television series were made out of vaccuformed plastic Tenmille gauge 1 kits. The company still exists today, but the vaccuformed kits have been replaced with more accurate laser cut wood versions.

Two original Troublesome Truck face masks are now owned by Twitter user ThomasTankMerch.